Network Working Group T. Narten
Request for Comments: 3041 IBM
Category: Standards Track R. Draves
Microsoft Research
January 2001
Privacy Extensions for Stateless Address Autoconfiguration in IPv6
Status of this Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2001). All Rights Reserved.
Abstract
Nodes use IPv6 stateless address autoconfiguration to generate
addresses without the necessity of a Dynamic Host Configuration
Protocol (DHCP) server. Addresses are formed by combining network
prefixes with an interface identifier. On interfaces that contain
embedded IEEE Identifiers, the interface identifier is typically
derived from it. On other interface types, the interface identifier
is generated through other means, for example, via random number
generation. This document describes an extension to IPv6 stateless
address autoconfiguration for interfaces whose interface identifier
is derived from an IEEE identifier. Use of the extension causes
nodes to generate global-scope addresses from interface identifiers
that change over time, even in cases where the interface contains an
embedded IEEE identifier. Changing the interface identifier (and the
global-scope addresses generated from it) over time makes it more
difficult for eavesdroppers and other information collectors to
identify when different addresses used in different transactions
actually correspond to the same node.
Narten & Draves Standards Track [Page 1]RFC 3041 Extensions to IPv6 Address Autoconfiguration January 2001Table of Contents
1. Introduction............................................. 2
2. Background............................................... 3
2.1. Extended Use of the Same Identifier................. 3
2.2. Address Usage in IPv4 Today......................... 4
2.3. The Concern With IPv6 Addresses..................... 5
2.4. Possible Approaches................................. 6
3. Protocol Description..................................... 7
3.1. Assumptions......................................... 8
3.2. Generation Of Randomized Interface Identifiers...... 9
3.3. Generating Temporary Addresses...................... 10
3.4. Expiration of Temporary Addresses................... 11
3.5. Regeneration of Randomized Interface Identifiers.... 12
4. Implications of Changing Interface Identifiers........... 13
5. Defined Constants........................................ 14
6. Future Work.............................................. 14
7. Security Considerations.................................. 15
8. Acknowledgments.......................................... 15
9. References............................................... 15
10. Authors' Addresses....................................... 16
11. Full Copyright Statement................................. 17
1. Introduction
Stateless address autoconfiguration [ADDRCONF] defines how an IPv6
node generates addresses without the need for a DHCP server. Some
types of network interfaces come with an embedded IEEE Identifier
(i.e., a link-layer MAC address), and in those cases stateless
address autoconfiguration uses the IEEE identifier to generate a 64-
bit interface identifier [ADDRARCH]. By design, the interface
identifier is likely to be globally unique when generated in this
fashion. The interface identifier is in turn appended to a prefix to
form a 128-bit IPv6 address.
All nodes combine interface identifiers (whether derived from an IEEE
identifier or generated through some other technique) with the
reserved link-local prefix to generate link-local addresses for their
attached interfaces. Additional addresses, including site-local and
global-scope addresses, are then created by combining prefixes
advertised in Router Advertisements via Neighbor Discovery
[DISCOVERY] with the interface identifier.
Not all nodes and interfaces contain IEEE identifiers. In such
cases, an interface identifier is generated through some other means
(e.g., at random), and the resultant interface identifier is not
globally unique and may also change over time. The focus of this
document is on addresses derived from IEEE identifiers, as the